The pattern and time frame of sea sculpin adaptation to the freshwater lifestyle are shown. The major factors that drive this process are the forced invasion in fresh waters due to climate cooling ...and the migration of postlarval juveniles from more complex coastal biocenoses to estuaries and lower reaches of rivers. The ranges of two phylogenetic lineages of sculpins (autochthonous Asian and its Arctic derivative) were divided into three parts by the isolation of the Sea of Japan at the Pliocene–Pleistocene boundary: in the Sea of Okhotsk, in the Sea of Japan, and south of it. The different habitat conditions for the isolates that persisted for a long period of time caused three new taxa to form in the first lineage and four in the second. The ancestral branch of sculpins yielded
Trachidermus fasciatus
in the East China Sea,
Rheopresbe kazika
in the Sea of Japan, and
Mesocottus haitej
in the Sea of Okhotsk; the Arctic branch that derived from it, respectively, formed
Cottus reinii
in the East China Sea,
C. czerskii
and
C. hangiongensis
in the Sea of Japan, and
C. amblystomopsis
in the Sea of Okhotsk. During the Pleistocene isolations of the Sea of Japan and sculpin migrations induced by climate fluctuations,
C. pollux
separated from
C. reinii
in the southern Sea of Japan, while the southernmost freshwater populations of the amphidromous
C. amblystomopsis
and
C. hangiongensis
speciated into
C. nozawae
and
C. koreanus
, respectively.
The sculpins Cottus metae and C. scaturigo have previously been distinguished morphologically from C. gobio and described as distinct species. In the present study, sculpin samples from numerous ...sites covering the proposed range of C. metae and C. scaturigo, including unexamined adjacent sites that include topotypic specimens and other sculpins, were examined to determine whether they represent phylogenetically distinct units and to determine the geographical limits of the distribution of C. metae. Using two types of marker—the mitochondrial control region and the nuclear large subunit of the ribosomal RNA gene—we found high statistical support for C. gobio and C. metae forming two distinct clades. A sister relationship between C. gobio and C. metae was observed but also indicating, by analogy to the well‐established status of the former, that the latter is a distinct species. However, this conclusion does not apply to C. scaturigo as the sample from the type locality clustered with C. gobio. A survey of numerous sculpin localities in Slovenia and adjacent areas, including the Drava river system, found that C. metae populates only the Sava river system, from the headwaters in NW Slovenia to the Medveščak Stream at Zagreb, Croatia. However, further downstream in the Kolpa River, and also in the Lonja and Una river systems, the next two tributaries to the Sava River, a sculpin population genetically distinct from both C. metae and C. gobio was found.
Using mtDNA and nuclear LSU rRNA, we found a distinct position of Cottus metae relative to its neighboring sculpin populations. Cottus scaturigo did not show genetic distinctiveness and clustered within C. gobio. Cottus metae populates only the Sava river system, from the headwaters in Slovenia to the Medveščak Stream at Zagreb, Croatia. In the Kolpa River, and further downstream, we found a sculpin population genetically distinct from C. metae and C. gobio.
Movement of nutrients across ecosystem boundaries can have important effects on food webs and population dynamics. An example from the North Pacific Rim is the connection between productive marine ...ecosystems and freshwaters driven by annual spawning migrations of Pacific salmon (Oncorhynchus spp). While a growing body of research has highlighted the importance of both pulsed nutrient subsidies and disturbance by spawning salmon, their effects on population densities of vertebrate consumers have rarely been tested, especially across streams spanning a wide range of natural variation in salmon densities and habitat characteristics. We studied resident freshwater prickly (Cottus asper), and coastrange sculpins (C. aleuticus) in coastal salmon spawning streams to test whether their population densities are affected by spawning densities of pink and chum salmon (O. gorbuscha and O. keta), as well as habitat characteristics. Coastrange sculpins occurred in the highest densities in streams with high densities of spawning pink and chum salmon. They also were more dense in streams with high pH, large watersheds, less area covered by pools, and lower gradients. In contrast, prickly sculpin densities were higher in streams with more large wood and pools, and less canopy cover, but their densities were not correlated with salmon. These results for coastrange sculpins provide evidence of a numerical population response by freshwater fish to increased availability of salmon subsidies in streams. These results demonstrate complex and context-dependent relationships between spawning Pacific salmon and coastal ecosystems and can inform an ecosystem-based approach to their management and conservation.
The European bullhead (Cottus gobio) is widely distributed across Europe, and within the UK is native to England and Wales, where it is protected under the Habitats Directive. In Scotland, however, ...the species is considered invasive and thriving populations are recorded in the Forth and Clyde river catchments, and the Ale Water in the Scottish Borders. The genetic identity of the Scottish populations has not been established. There is also debate about the status of the European bullhead and its validity as single species, a species complex with several unresolved species, or distinct different species in its European distribution range. There is therefore a need to determine the taxonomy and likely source of the novel Scottish populations. Genetic analyses using cytochrome oxidase 1 (COI) mitochondrial DNA sequences were undertaken on specimens from the Forth and Clyde catchments, and combined with the results of morphological characteristics to provide a comprehensive assessment of the taxonomic classification for Scottish bullheads. There was considerable variation in morphological characteristics between populations within Scotland and a wider range of variability than previously recorded for English populations. Genetically the Scottish populations were very closely related to English specimens, supporting the hypothesis of introduction directly from England to Scotland. In terms of broader relationships, Scottish specimens are genetically more closely related to the ostensible species Chabot fluviatile Cottus perifretum, which has been suggested as one of a complex of species across Europe. Morphologically they exhibit characteristics on the spectrum between C. perifretum and C. gobio. There is an urgent need for the clarification of the taxonomy of Cottus sp(p). to avoid confusion in future publications, legislation and management practices relating to bullheads throughout the UK and Europe.
Environmental DNA (eDNA) is revolutionizing biodiversity monitoring, occupancy estimates, and real-time detections of invasive species. In the Great Lakes, the round goby (Neogobius melanostomus), an ...invasive benthic fish from the Black Sea, has spread to encompass all five lakes and many tributaries, outcompeting or consuming native species; however, estimates of round goby abundance are confounded by behavior and habitat preference, which impact reliable methods for estimating their population. By integrating eDNA into round goby monitoring, improved estimates of biomass may be obtainable. We conducted mesocosm experiments to estimate rates of goby DNA shedding and decay. Further, we compared eDNA with several methods of traditional field sampling to compare its use as an alternative/complementary monitoring method. Environmental DNA decay was comparable to other fish species, and first-order decay was lower at 12°C (k = 0.043) than at 19°C (k = 0.058). Round goby eDNA was routinely detected in known invaded sites of Lake Michigan and its tributaries (range log10 4.8-6.2 CN/L), but not upstream of an artificial fish barrier. Traditional techniques (mark-recapture, seining, trapping) in Lakes Michigan and Huron resulted in fewer, more variable detections than eDNA, but trapping and eDNA were correlated (Pearson R = 0.87). Additional field testing will help correlate round goby abundance with eDNA, providing insight on its role as a prey fish and its impact on food webs.
Understanding the genomic basis of adaptive divergence in the presence of gene flow remains a major challenge in evolutionary biology. In prickly sculpin (Cottus asper), an abundant euryhaline fish ...in northwestern North America, high genetic connectivity among brackish‐water (estuarine) and freshwater (tributary) habitats of coastal rivers does not preclude the build‐up of neutral genetic differentiation and emergence of different life history strategies. Because these two habitats present different osmotic niches, we predicted high genetic differentiation at known teleost candidate genes underlying salinity tolerance and osmoregulation. We applied whole‐genome sequencing of pooled DNA samples (Pool‐Seq) to explore adaptive divergence between two estuarine and two tributary habitats. Paired‐end sequence reads were mapped against genomic contigs of European Cottus, and the gene content of candidate regions was explored based on comparisons with the threespine stickleback genome. Genes showing signals of repeated differentiation among brackish‐water and freshwater habitats included functions such as ion transport and structural permeability in freshwater gills, which suggests that local adaptation to different osmotic niches might contribute to genomic divergence among habitats. Overall, the presence of both repeated and unique signatures of differentiation across many loci scattered throughout the genome is consistent with polygenic adaptation from standing genetic variation and locally variable selection pressures in the early stages of life history divergence.
Plastic pollution has become a pervasive environmental problem on a global scale, from the ocean depths to the aquatic ecosystems of the Tibetan Plateau. To date, data on plastic and microplastic ...occurrence in pristine ecosystems like high-mountain lakes are lacking. In this study, plastic (>5000 μm) and microplastic (10–5000 μm) levels were measured in snow at the end of the winter season (April 2020), and in water, sediment, and biological samples collected monthly (June–October 2019) during the ice-free season from the Dimon Lake, a high-mountain lake in the Carnic Alps, northeast Italy. Biological samples consisted of chironomids (Diptera, Chironomidae; n = 150) and stomach contents of Cottus gobio (n = 40). Analysis of the water, sediment, and biological samples revealed the absence of plastic and microplastics larger than 10 μm, whereas the snow samples contained microplastics of polyethylene terephthalate (PET) albeit at very low levels (0.11 ± 0.19 L-1). These results show that while the lake ecosystem could be considered unpolluted by microplastics, abundant snow precipitation in winter can trap microplastic particles that deposit on the ground. The very low levels of PET microparticles recorded in the snow samples suggest the need for further research to better understand the source of microplastic pollution in this environmental matrix.
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•Plastic and microplastic were measured in a high-mountain-lake from Carnic Alps.•Water, sediment, macroinvertebrates, fish and snow samples were analyzed.•No microplastics (10–5000 μm) were detected in the biotic and abiotic samples.•Microplastics were detected only in the snow: PET levels of 0.11 ± 0.19 items L−1.•No macro- and mesoplastics (>5000 μm) were found in this remote ecosystem.
Freshwater sculpins, grouped by their common ecological characteristic of freshwater habitats, comprise the species from the genera Cottus, Trachidermus, Mesocottus and Myoxocephalus as well as the ...Baikal sculpins. These fishes are typically coldwater-adapted, having probably originated polyphyletically from ancestral species of marine sculpins. Gottus, the most speciose taxonomic group, includes at least 64 species and is distributed throughout the fresh waters of the northern part of the Northern Hemisphere. Indinidual species have diverse life histories, such as fluvial, lacustrine, catadromous, and freshwater amphidromous. The second most abundant group, the Baikal sculpins, includes 33 species in 12 genera representing 3 families, and comprises many benthic, and a few bentho-pelagic and pelagic species. The freshwater sculpins belonging to Trachidermus, Mesocottus and Myoxocephalus include only one or two species in each genus. Recent molecular phylogenetic analyses of Cottus species, Baikal sculpins and their relatives have demonstrated mainly that (1) Cottus kazika is a sister taxon to Trachidermus fasciatus (designated lineage A), (2) Cottus species, except for C. kazika, and the Baikal sculpins are monophyletic, (3) on the basis of (1) and (2), Cottus as presently recognized is not monophyletic, and (4) the Major monophyletic lineages include 7 lineages: lineage B from Eurasia, lineages C and D from East Asia, the Cottopsis clade (sensu Copeia 2005:303–311, 2005) from the west coast of North America, the Cottus clade from the Circum-Arctic sea, the monophyletic Baikal sculpins, and the Uranidea clade. These findings suggested that the monophyletic freshwater sculpins that comprise the lineage A and the 7 other lineages may undergone two major radiations, one having occurred in the fresh water Cottus species in the northern part of the Northern Hemisphere, and the other in the Baikal sculpins in the Lake Baikal, the world’s oldest freshwater lake. Through these adaptive radiations, a tremendous diversity of morphological, ecological, physiological and life historical traits now exists in the freshwater sculpins.
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